Defensive publication



DEFENSIVE PUBLICATION UNITED STATES PATENT OFFICE Published at therequest or the applicant or owner in accordance with the Notice of Apr.11, 1968, 849 0.G. 1221. Identification is by serial number of theapplication and the heading indicates the number of pages ofspecification, including claims, and oi! sheets of drawing contained inthe application as originally filed. The file of this application isavailable to the public for inspection; reproduction may he purchasedfor 30 cents per sheet.

Applications published under the Defensive Publication Program have notbeen examined as to the merits of alleged invention. The Patent Oflloemakes no assertion as to the novelty of the disclosed subject matter.

PUBLISHED SEPTEMBER 30, 1969 805,938 ACID-CATALYZED PROCESS FOR'CYCLODE- HYDRATION OF SHAPED POLYHYDRAZIDE STRUCTURES Donald RichardWilson, Wilmington, DeL, assignor to E. I. du Pont de Nemours andCompany, Wilmington, Del., a corporation of Delaware Continuation ofapplication Ser. No. 582,531, Sept. 28, 1966. This application Feb. 14,1969. Published Sept. 30, 1969 Int. Cl. C08g 33/04 US. Cl. 26078.4 NoDrawing. 12 Pages Specification An acid-catalyzed process for thecyclodehydration of shaped polyhydrazide structures, such as filaments,to the corresponding poly(1,3,4-oxadiazoles). The process comprisesincorporating into a shaped polyhydrazide structure between about 0.1and 5.5 mole percent of sulfonic, phosphonic, phosphonous, boronic,sulfuric or phosphoric acid, and heating the structure to a temperatureof between 170 C. and the melting point of the polyhydrazide for alength of time sufiicient to efiect substantially complete conversion ofthe polyhydrazide to the corresponding poly(1,3,4-oxadiazole).Preferably, the polyhydrazide is isophthaloyl terephthaloylcopolyhydrazide and the acid is benzenesulfonic acid. Preferably, thestructure is heated at a temperature of between 250 and 320 C.

